A sliding T bevel is an adjustable gauge for setting and transferring angles. The bevel has two main parts. There is an elongated blade, usually of metal, that has a slot along most of its length. There also is a swivel arm or handle, usually made of wood or plastic, which is connected is connected to the blade by a bolt that passes through the slot and which has a thumbscrew or wing nut. Upon loosening the thumbscrew the handle is positioned along the slot length and pivoted to an angle relative to the blade longitudinal axis. It is then locked in this position by tightening the thumbscrew.
Sliding T bevels are mostly used for measuring or transferring angles to be duplicated, such as the angle of the cut at the end of a board. In use, the blade is placed against the long edge of the board being measured and the thumbscrew is rotated to unlock the handle. While, the blade is held to the board edge the handle is moved to lie against the cut angle of the end of the board and is then locked into place. The angle measured can now be transferred to another piece of board whose end is intended to be cut at the same angle by placing the bevel on the new board.
If it is desired to measure and know the numerical value of the angle between the handle and the blade, then a protractor is often used with the sliding T bevel. While the use of the protractor in combination with the bevel accomplishes the desired purpose, it requires the use of two tools and making a separate measurement of the angle of the bevel handle. This is sometimes inconvenient to accomplish. Further, when using a mechanical type protractor it is sometimes difficult to obtain an angle measurement with the degree of accuracy desired, such as to one tenth of a degree. Digital protractors are available, such as one sold by General Tools & Instruments Co., LLC of New York, which can provide a more accurate angle readout. However, this still requires the purchase and use of two tools.
Therefore, it would be desirable to have a sliding T bevel in which the angle of the handle relative to the blade along which the handle slides and pivoted can be read out directly. This overcomes the disadvantages of having to have two tools and having to make a separate measurement of the angle at which the handle is fixed relative to the blade and can provide a more accurate measurement than is possible with a conventional mechanical protractor. The T bevel of the invention also eliminates the error that possibly could occur when using the protractor and eliminates the multiple errors possibly produced by the combined use of a standard T bevel and protractor.